Reversing valve

Short description: Valve that reverses flow direction in part of a circuit

A reversing valve removed from an HVAC heat pump for replacement

A reversing valve is a type of valve and is a component in a heat pump, that changes the direction of refrigerant flow. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a residence or facility to be heated and cooled by a single piece of equipment, by the same means, and with the same hardware.[1]

## Contents

* 1 Operation
* 2 Control
* 3 Replacement
* 4 See also
* 5 References

## Operation

The reversing valve has two states, relaxed (unactivated) versus energized. The energized state is typically achieved by applying 24 volts AC, which is commonly used in HVAC equipment. The heat pump can be designed by the manufacturer to produce either cooling or heating with the reversing valve in the relaxed state. When the reversing valve is energized, it will produce the opposite transfer of heat from its relaxed state. For example, a reversing valve installed in such a way as to produce cooling when relaxed will produce heating when energized. Likewise, a reversing valve installed to produce heating when relaxed will produce cooling when energized.

## Control

Depending on the construction and use of the heat pump, the reversing valve may be driven by the heat pump through the use of a defrost control board, or it may be driven directly by a thermostat (typically from the "O" terminal of the thermostat).

## Replacement

Reversing valves are built into the heat pump by the manufacturer, and must be replaced by an HVAC technician if they fail. Since the valve is an integral part of the sealed refrigerant circuit, proper procedures for recovering and then later refilling the refrigerant must be followed, to prevent its loss into the atmosphere.

## See also

* Thermostat
* Thermal expansion valve
* Freeze stat

## References

1. ↑ What is a Reversing Valve

* v
* t
* e

Heating, ventilation, and air conditioning

Fundamental concepts|

* Air changes per hour
* Bake-out
* Building envelope
* Convection
* Dilution
* Domestic energy consumption
* Enthalpy
* Fluid dynamics
* Gas compressor
* Heat pump and refrigeration cycle
* Heat transfer
* Humidity
* Infiltration
* Latent heat
* Noise control
* Outgassing
* Particulates
* Psychrometrics
* Sensible heat
* Stack effect
* Thermal comfort
* Thermal destratification
* Thermal mass
* Thermodynamics
* Vapour pressure of water

Technology|

* Absorption refrigerator
* Air barrier
* Air conditioning
* Antifreeze
* Automobile air conditioning
* Autonomous building
* Building insulation materials
* Central heating
* Central solar heating
* Chilled beam
* Chilled water
* Constant air volume (CAV)
* Coolant
* Dedicated outdoor air system (DOAS)
* Deep water source cooling
* Demand-controlled ventilation (DCV)
* Displacement ventilation
* District cooling
* District heating
* Electric heating
* Energy recovery ventilation (ERV)
* Firestop
* Forced-air
* Forced-air gas
* Free cooling
* Heat recovery ventilation (HRV)
* Hybrid heat
* Hydronics
* HVAC
* Ice storage air conditioning
* Kitchen ventilation
* Mixed-mode ventilation
* Microgeneration
* Natural ventilation
* Passive cooling
* Passive house
* Radiant heating and cooling system
* Radiant cooling
* Radiant heating
* Radon mitigation
* Refrigeration
* Renewable heat
* Room air distribution
* Solar air heat
* Solar combisystem
* Solar cooling
* Solar heating
* Thermal insulation
* Underfloor air distribution
* Underfloor heating
* Vapor barrier
* Vapor-compression refrigeration (VCRS)
* Variable air volume (VAV)
* Variable refrigerant flow (VRF)
* Ventilation

Components|

* Air conditioner inverter
* Air door
* Air filter
* Air handler
* Air ionizer
* Air-mixing plenum
* Air purifier
* Air source heat pumps
* Automatic balancing valve
* Back boiler
* Barrier pipe
* Blast damper
* Boiler
* Centrifugal fan
* Ceramic heater
* Chiller
* Condensate pump
* Condenser
* Condensing boiler
* Convection heater
* Compressor
* Cooling tower
* Damper
* Dehumidifier
* Duct
* Economizer
* Electrostatic precipitator
* Evaporative cooler
* Evaporator
* Exhaust hood
* Expansion tank
* Fan coil unit
* Fan filter unit
* Fan heater
* Fire damper
* Fireplace
* Fireplace insert
* Freeze stat
* Flue
* Freon
* Fume hood
* Furnace
* Furnace room
* Gas compressor
* Gas heater
* Gasoline heater
* Geothermal heat pump
* Grease duct
* Grille
* Ground-coupled heat exchanger
* Heat exchanger
* Heat pipe
* Heat pump
* Heating film
* Heating system
* High efficiency glandless circulating pump
* High-efficiency particulate air (HEPA)
* High pressure cut off switch
* Humidifier
* Infrared heater
* Inverter compressor
* Kerosene heater
* Louver
* Mechanical fan
* Mechanical room
* Oil heater
* Packaged terminal air conditioner
* Plenum space
* Pressurisation ductwork
* Process duct work
* Radiator
* Radiator reflector
* Recuperator
* Refrigerant
* Register
* Reversing valve
* Run-around coil
* Scroll compressor
* Solar chimney
* Solar-assisted heat pump
* Space heater
* Smoke exhaust ductwork
* Thermal expansion valve
* Thermal wheel
* Thermosiphon
* Thermostatic radiator valve
* Trickle vent
* Trombe wall
* Turning vanes
* Ultra-low particulate air (ULPA)
* Whole-house fan
* Windcatcher
* Wood-burning stove

Measurement
and control|

* Air flow meter
* Aquastat
* BACnet
* Blower door
* Building automation
* Carbon dioxide sensor
* Clean Air Delivery Rate (CADR)
* Gas sensor
* Home energy monitor
* Humidistat
* HVAC control system
* Intelligent buildings
* LonWorks
* Minimum efficiency reporting value (MERV)
* OpenTherm
* Programmable communicating thermostat
* Programmable thermostat
* Psychrometrics
* Room temperature
* Smart thermostat
* Thermostat
* Thermostatic radiator valve

Professions, trades,
and services|

* Architectural acoustics
* Architectural engineering
* Architectural technologist
* Building services engineering
* Building information modeling (BIM)
* Deep energy retrofit
* Duct leakage testing
* Environmental engineering
* Hydronic balancing
* Kitchen exhaust cleaning
* Mechanical engineering
* Mechanical, electrical, and plumbing
* Mold growth, assessment, and remediation
* Refrigerant reclamation
* Testing, adjusting, balancing

Industry organizations|

* ACCA
* AHRI
* AMCA
* ASHRAE
* ASTM International
* BRE
* BSRIA
* CIBSE
* Institute of Refrigeration
* IIR
* LEED
* SMACNA

Health and safety|

* Indoor air quality (IAQ)
* Passive smoking
* Sick building syndrome (SBS)
* Volatile organic compound (VOC)

See also|

* ASHRAE Handbook
* Building science
* Fireproofing
* Glossary of HVAC terms
* World Refrigeration Day

* Template:Home automation
* Template:Solar energy

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